The present invention relates generally to a palletized seating system, and more particularly to a latching palletized seating system specifically adapted for use on aircraft to allow quick removal of palletized seats, to thereby enable an aircraft to be converted from a passenger aircraft to a freight aircraft and vice versa.
Aircraft are used in a wide variety of applications to transport individuals as well as freight. It is highly desirable to be able to use the aircraft for either application. To this end, various forms of cargo latching systems have been developed to allow quick and easy removal of pallets upon which are mounted one or more seats of an aircraft. Once the pallets containing the seats have been removed, the fuselage of the aircraft can be used to carry cargo instead of individual passengers. One such patent directed to a pallet latching system is U.S. Pat. No. 3,381,921 assigned to the Boeing Company. This patent involves the use of a plurality of longitudinally aligned rail assemblies mounted in the floor of the aircraft. Each rail assembly comprises a plurality of elongated base sections having a plurality of anchoring elements located at closely spaced longitudinal intervals therealong. Each rail assembly also has a plurality of pallet conveying rollers which are located laterally of the seat pallet anchoring elements and spaced at suitable intervals longitudinally therealong to provide a substantially continuous pallet conveying surface or plane located just above the rail assembly. A plurality of retractable cargo pallet latch units are mounted to a lower part of a seat pallet. The seat pallet is able to be rolled along the rollers of the rail assembly to a desired position and then latched in place via engagement of the latching mechanism with one of the anchoring elements.
While the above arrangement has proven effective for its intended use, it is nevertheless necessary to provide a latch design that meets new and increased requirements for maintaining palletized seats restrained to the floor structure of an aircraft in the event of floor deformations caused by emergency landing conditions, and to ensure adequate visual indication of proper engagement of the latching mechanism when the mechanism is in a latched position. More specifically, a latching mechanism is needed which operates to positively restrain the palletized seats to the floor of the aircraft in both fore and aft directions during emergency landing conditions while still maintaining the ability of the pallets to be quickly installed and removed when it is desired to convert the aircraft from a passenger aircraft to a freight aircraft, or vice versa.
Still further, a latching mechanism is needed which provides the above benefits but which does not unduly increase turnaround time for converting the aircraft between passenger and freight applications, and which does not allow the seats to move or rattle in a manner which would be objectionable to passengers when the aircraft is in a passenger carrying configuration.
The above and other objects are provided by a palletized seat latching mechanism in accordance with preferred embodiments of the present invention. In one preferred embodiment the latching mechanism incorporates a first pawl and a second pawl both pivotably disposed within a frame. Each pawl further includes camming surfaces which contact each other as the first pawl is moved from an unlocked position into a locked position relative to one of a plurality of restraining pins of a conventional support rail assembly secured to the floor of the aircraft. The first pawl functions to restrain a pallet to which it is secured against forward movement. The camming surfaces operate to cause the first pawl to urge the second pawl into locked engagement with a separate restraining pin as the first pawl is moved into its locked position. The second pawl restrains the seat pallet from moving in the aft direction. Advantageously, if either one of the pawls is not fully engaged with its respective restraining pin when the latching mechanism is secured to the rail assembly, the entire pallet will tend to rise or xe2x80x9cbowxe2x80x9d upwardly from the rail assembly, thus presenting a visual cue that the mechanism is not fully secured to the restraining pins of the rail assembly. This condition will also dramatically increase the force required to lock the pallet, thus providing a tactile clue that one of the pawls is not properly engaged. Torsion springs associated with each of the first and second pawls serve to tend to bias the pawls into an unlocked position. However, when the first pawl is urged into a locked position, it cammingly urges the second pawl substantially simultaneously into a locked position relative to a separate restraining pin.
In the preferred embodiments, one of the pawls incorporates a handle which can be grasped by a user to lock and unlock the latching mechanism from the rail assembly. The handle incorporates a safety latching assembly which serves to lock the handle to a secondary restraining pin carried on a frame portion of the latching mechanism such that the handle cannot be accidentally lifted without first disengaging a separate safety pawl carried by the handle. The safety latching mechanism also serves to automatically secure the handle in its locked position when the handle is urged into this position by the user without the user having to manipulate the safety pawl. When the handle is to be opened (i.e., to place the latching mechanism in an unlocked state), a simple tool such as a screwdriver is required to unlatch the safety pawl before the handle can be lifted into the unlocked position.
The latching mechanism of the present invention thus forms a simple yet effective means for restraining a palletized seat structure from both forward and aft movement during operation of the aircraft. The dual pawls of the latching mechanism further serve to ensure that the latching mechanism will not become disengaged from its associated rail assembly even in the event of flexing of the floor of the aircraft during an emergency landing procedure. The latching mechanism of the present invention further does not require significant modification to a standard palletized seat structure or to conventional rail assemblies used in present day aircraft in connection with palletized seat systems.